The present invention relates to a catheter assembly for delivering liquids to the blood stream of a patient, and more particularly, concerns an infusion catheter assembly constructed to pre-dilute parenteral liquids prior to being delivered to the vein of a patient.
Standard intravenous catheters for delivering parenteral liquids into the blood stream of a patient are generally formed with a single liquid outlet at the catheter tip. If a hypertonic solution, total parenteral nutrition liquid or the like is administered through such a catheter, the blood in the immediate vicinity of the catheter outlet receives this liquid. At this point, the infusion liquid is at its highest concentration and, as a result, may cause some complications. Specifically, depending upon the constituents of the infusion solution, irritation of the vein may ensue, inflammation or swelling is possible along with potential vein necrosis, as well as infusion phlebitis due to the hypertonic nature of the infusion solution. With this in mind, it has become common practice to avoid the peripheral veins as much as possible in administering these types of liquids in order to reduce the incidence of phlebitis. For example, a vein, usually sub-clavian, jugular or other central vein, with a large volume of blood flow is selected to provide rapid dilution of the infusion solution in the area of the outlet. It is appreciated that this practice, the insertion of the catheter into a central vein, is much more difficult than insertion into a peripheral vein, and is potentially more harmful since the incidence of infection and other complications is often greater in the central veins. Accordingly, the need for a catheter to deliver diluted infusion solution, particularly to a peripheral vein, has been established, while the satisfactory fulfillment of that need is still being sought.
An arterial infusion catheter disclosed in U.S. Pat. No. 3,888,249 is directed to a catheter design which seeks to improve the mixing of the medication as it is delivered to the bloodstream. This patented invention relies upon a single flexible catheter tube with one or more slits therein which serve as a one-way valve. However, sufficient positive pressure inside the catheter is needed to inject the diffused medication into the bloodstream of the patient. Also, infusion solution at full concentration may impinge on the vein wall.
Other catheter devices and techniques to pre-dilute the infusion solution as it is delivered to the patient are still in demand, and it is to that end which the present invention is directed.